Method of making a thin film magnetic head assembly with multiconductive connecting elements

ABSTRACT

A method of making a thin film magnetic head assembly having a substrate, superstrate and thin film magnetic transducer mounted therebetween wherein the thin film magnetic transducer includes conductive leads located interior to and extending between the substrate and superstrate comprising the steps of mounting a thin film transducer on the substrate with the transducing portion thereof located adjacent one edge of the substrate, positioning a preformed planar conductive connecting member formed of an elongated support section and a plurality of spaced, aligned connecting elements having a relatively thin coating of diffusable conductive metal coating located on one side positioned in intimate contact with the conductive leads with the connecting elements and the elongated support section extending passed the substrate, placing a superstrate in alignment with the substrate, thin film magnetic transducer and planar conductive connecting member with the surface thereof in intimate engagement with the connecting elements to form a sub-assembly thereof having a predetermined space which has a dimension equal to the sum of the thickness of one of the conductive leads, the planar conductive connecting member and the thickness of the diffusable conductive metal coating thereon, placing a quantity of insulating material adjacent the spaced opposed edges and in the vicinity of the transducing portion of the thin film magnetic transducer, heating the sub-assembly, urging the superstrate and the substrate together with a clamping force enabling the diffusable conductive metal coating to diffuse into both the conductive leads and connecting elements.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a new and novel method of manufacturing a thinfilm magnetic head assembly having a thin film magnetic transducer,substrate, superstrate and connecting elements joined to conductiveleads of the thin film magnetic transducer by a diffused electricalconnection formed of a diffusable conductive metal layer by use of aplanar conductive connecting member used as a spacer and by heating,clamping and maintaining the so clamped sub-assembly at a predeterminedbonding temperature for a selected time period to enable a preformedglass layer by capillary action to encapsulate the thin film magnetictransducer, and the conductive leads and connecting elements joinedtogether by a diffused electrical connection and bond the same into anintegral thin film head assembly.

2. Disclosure of the Prior Art

It is known in the prior art to manufacture ferrite magnetic headshaving at least two pole pieces formed of sintered ferromagnetic oxidematerial wherein the pole pieces are joined together with a short gaptherebetween to from the transducing portion thereof and wherein thepole pieces are bonded together by glass. Typical of such known methodsare the methods disclosed in U.S. Pat. Nos. 3,577,634; 3,246,383 and3,024,318. Magnetic heads manufactured by the above known methods arecombined with housings or ceramic sliders to form magnetic headassemblies used in apparatus, systems and equipment for storing andretrieving information in a recording media.

In order to produce smaller magnetic head assemblies, reduce the size ofthe gap forming the transducing portion of such magnetic head assembliesand to increase the recording densities and decrease the track widths ofsuch magnetic head assemblies, new techniques have been developed toproduce thin film magnetic transducers. Such thin film magnetictransducers can be fabricated by use of known vapor deposition,sputtering or plating techniques. Typical of such thin film magnetictransducers produced by use of the vapor deposition techniques are thosedisclosed in U.S. Pat. Nos. 3,867,368 and 3,846,841. Other thin filmtransducers are disclosed in U.S. Pat. Nos. 4,052,749 and 4,092,688.

With the rapid advance in techniques for manufacturing thin filmmagnetic transducers, the prior art includes many known techniques forfabricating the thin film magnetic head assemblies using thin filmmagnetic transducers. Typically, epoxy, glass bonding and otheradhesives are used to form an integral bonded thin film magnetic headassembly.

One such glass bonding technique is disclosed in U.S. Pat. Nos.4,143,458 and 4,191,983 to George W. Gibson, and assigned to the sameAssignee as is this present invention.

SUMMARY OF THE INVENTION

The present invention discloses, teaches and claims a significantimprovement in fabrication and assembly of thin film magnetic headassemblies using a thin film, vapor deposited, magnetic transducer.

Gibson in U.S. Pat. No. 4,143,458 discloses that known thin filmmagnetic transducers when heated to a temperature above 500° C. causesirreversible damage to the magnetic and/or electrical characteristics ofthe thin film magnetic transducer causing the same to be permanentlydestroyed. Thus, the temperature at which either the magnetic orelectrical characteristics of the thin film transducer would be affectedestablishes a thermal stress temperature which cannot be exceeded duringfabrication of thin film magnetic head assemblies.

The use of glass bonding techniques in certain of the above referencedU.S. patents for fabricating ferrite poles pieces use glass materialsthat have melting temperatures in the order of 900° C. to insure thatthe coefficient of expansions of the ferrite and glass insulating andbonding material are substantially the same.

In the method of making a thin film magnetic head assembly disclosed inthe above referenced U.S. Pat. No. 4,143,458, the use of a glass bondingmaterial having a melting point below the thermal stress temperature isdisclosed. A glass bonding material in the form of a thin rod locatedexterior to the assembly formed of the substrate, superstrate and thinfilm magnetic transducer is drawn into a cavity within the assembly bycapillary action. The glass bonding material and the assembly aremaintained at a bonding temperature located in a temperature range ofthe melting point of the glass material and the thermal stresstemperature. The cavity within the assembly was formed by means of aspacing member. In order to insure that conductive leads from the thinfilm transducer were not encapsulated in the glass bonding material andwould be accessable for attachment of connecting leads or elementsthereto, the quantity of glass materially drawn in to the cavity had tobe precisely controlled.

The present invention teaches a novel and unique method of assembling athin film magnetic head assembly by using a substrate, thin filmmagnetic transducer, superstrate, a quantity of insulating glassmaterial preferably in the form of a thin glass rod and a planarconductive connecting member having connecting elements wherein at leastone surface thereof has a diffusable conductive metal coating layerformed thereon which when the sub-assembly compounds are heated in apreselected atmosphere which inhibits oxidation and corrosion of thesub-assembly components to a selected bonding temperature and whensubjected to a clamping force during the heating to the bondingtemperature and subsequent maintaining of the assembly at the bondingtemperature for a predetermined period of time results in a glass bondedthin film magnetic head assembly wherein both the thin film magnetictransducer and conductive leads thereof electrically connected togetherby a diffused electrical connection are encapsulated by the glassbonding material.

One advantage of the present invention is that the method for making thethin film magnetic head assemblies results in the conductive leads ofthe thin film magnetic transducers used therein being positively andelectrically joined to connecting members and that electrical connectionbeing encapsulated by the glass bonding material to insure ahermatically sealed connection.

Another advantage of the present invention is the the connecting membersextend from the thin film magnetic head assembly and are adapted to haveelectrical connectors affixed thereto rather than directly to the thinfilm magnetic transducer as is necessary in certain of the prior arthead assemblies.

A further advantage of the present invention is that by use of apreformed planar conductive connecting member, the thin film magnetichead assemblies can be fabricated with the connecting elements of theplanar conductive connecting member held in place during themanufacturing process and when completed, a support section thereof iseasily removed resulting in easily accessable connecting elementsadapted to have external electrical leads connected thereto withoutexposing the conductive leads and thin film magnetic transducers toexternal conditions such as overheating during soldering of theelectrical leads to the connecting elements.

BRIEF DESCRIPTION OF THE DRAWING

The foregoing and other advantages and features of the invention willbecome apparent from the following features of the preferred embodimentwhen considered together with the illustrations in the accompanyingdrawings which include the following figures:

FIG. 1 is a pictorial diagram of a thin film magnetic transducer mountedon a selected surface of a substrate;

FIG. 2 is a schematic representation of a substrate surface having aplurality of space aligned thin film magnetic transducers depositedthereon wherein each thin film magnetic transducer has a threeconductive leads extending therefrom;

FIG. 3 is a pictorial representation of a preformed planar conductiveconnecting member having a support section and a plurality of connectingelements extending substantially perpendicular therefrom and wherein thebottom surface of the connecting elements have a relatively thindiffusable conductive metal coating formed thereon;

FIG. 4 is a pictorial representation of the positioning of the planarconductive connecting member relative to the conductive leads of thethin film magnetic transducer and with the diffusable conductive metallayer of the connecting elements in intimate engagement with theconductive leads;

FIG. 5 is a pictorial representation of the placing of the superstrateinto alignment in order to place the same into intimate engagement ofthe sub-assembly of illustrated in FIG. 4;

FIG. 6 is pictorial representation of the final relationship between thesub-assembly of FIG. 4 and the superstrate of FIG. 5 with a thin glassrod of insulating glass material positioned adjacent the predeterminedspace and with a clamping action being urged against the substrate andsuperstrate;

FIG. 7 is a schematic representation of a glass bonded thin filmmagnetic head assembly with the thin film magnetic transducer and thediffused electrical connection between the conductive leads and theconnecting elements encapsulated with the glass bonding insulatinglayer;

FIG. 8 is a pictorial representation of the positioning of the planarconductive connecting member relative to the conductive leads of thethin film magnetic transducer and with the diffusable conductive metallayer of the connecting elements in intimate engagement with theconductive leads;

FIG. 9 is pictorial representation of the final relationship between theconductive leads and the connecting elements with the support sectionremoved;

FIG. 10 is a schematic representation of a glass bonded thin filmmagnetic head assembly with the thin film magnetic transducer and thediffused electrical connection between the conductive leads and theconnecting elements encapsulated with the glass bonding insulatinglayer;

FIG. 11 is a schematic representation of a lapped thin film magnetictransducer of FIG. 10;

FIG. 12 is a pictorial representation of a top view of anotherembodiment of a thin film transducer which may be fabricated into a thinfilm magnetic head assembly using the teachings of this invention;

FIG. 13 is a pictorial representation of a plan view in cross-section ofanother embodiment of a lapped thin film magnetic head assembly usingthe teachings of theis invention; and

FIG. 14 is an enlarged pictorial representation partially incross-section showing the small gap of the transducing portion of theembodiment illustrated in FIG. 13.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 to 8, inclusive, show a method of making a thin film magnetichead assembly having a substrate, superstrate and thin film magnetictransducer mounted therebetween wherein the thin film magnetictransducer may be fabricated by any known vapor deposition, sputteringor plating techniques. In the preferred embodiment of the presentinvention a substrate 20 is adapted to have a thin film magnetictransducer, shown generally by arrow 22, affixed thereto. The thin filmmagnetic transducer 22 illustrated in FIG. 1 has a lower pole piece 24,an upper pole piece 26 and a gap which is formed to have a preselectedlength. In a typical embodiment, the gap has a dimension in the order ofabout one micron or less. Depending upon the techniques used tofabricate the thin film magnetic transducer, an insulating material 30may be deposited in the gap, which is illustrated as insulated gap 28,and may fill the space between the gap and a coil stack 32. In theembodiment illustrated in FIG. 1, the thin film magnetic transducer hasa plurality of stacked coil windings 32. However, the thin film magnetictransducer may have a planar spiral coil structure. Therefore, theconstruction of the thin film magnetic transducer is not essential tothe method of this invention and any thin film transducer may be used impracticing this invention. For example, thin film magnetoresistivetransducers may be used to fabricate thin film head assemblies using theteachings of the present invention.

Typically the thin film magnetic transducer includes a transducingportion formed by lower pole piece 24 and upper pole piece 26 to definethe gap 28. In FIG. 1, the transducing portion is located exterior toadjacent edges of the substrate 20. The thin film magnetic transducerhas a plurality of conductive leads illustrated as 38 extendingtherefrom. Preferably, the conductive leads are of sufficient length toat least extent to another edge of the substrate other that the edgehaving the transducing portion of the thin film magnetic transducer.

In practicing the method of the present invention, the step of mounting,on a selected surface of the substrate 20, a thin film magnetictransducer 22 with the transducing portion thereof located adjacent oneedge of the substrate 22 which intersects with said selected surface.

FIG. 2 illustrates the use of a single substrate 20 which has aplurality of spaces aligned identical thin film transducers affixedthereto wherein the upper pole piece 26, windings 40 and threeconductive leads 38, 42 and 44 extending therefrom. The other identicaltransducers likewise have similar elements, the upper pole piece 28',coil windings 40, and conductive leads 38' 42' being typical. In a batchfabrication process, typically a plurality of thin film transducers areformed on a single substrate and are maintained in the form duringmanufacturing. When the thin film magnetic transducers are completed,the finished head assemblies are cut or sliced into individualcomponents.

FIG. 3 illustrates the construction of the preferred embodiment of apreformed planar conductive connecting member. The preformed planarconductive member has a thickness at least equal to that of the thinfilm magnetic transducer 22. As illustrated in FIG. 3, the planarconductive connecting member is formed of an elongated support section60 and a plurality of spaced, aligned connecting elements 62, 64 and 66or 62', 64' or 66' 68 extending substantially perpendicular from theelongated support section 60. In the preferred embodiment, the spacings70 between connecting elements 62, 64 and 68 are substantially equal tothe spacings between the conductive leads 38, 42 and 44 illustrated inFIG. 2. An indexing opening 72 has a dimension equal to the spacings ofthe thin film magnetic transducers on a single substrate 20 to enablebatch assembly of the thin film magnetic head assemblies.

As shown in FIG. 4, the connecting elements 62, 64 and 66 include arelatively thin diffusable conductive metal coating 68 located on oneside thereof. In this embodiment, the metal coating 68 extends to thesupport section 60, although that is not necessary, but desireable.

In FIG. 5, a superstrate 44 is adapted to be positioned in alignmentwith the sub-assembly of FIG. 4. The surface of the superstrate 44 isplanar in shape.

Referring to the step illustrated in FIG. 6, the step includes placingthe superstrate 44 in alignment with the substrate 20, the thin filmmagnetic transducer 22 and the planar conductive connecting member suchthat the one edge of the superstrate 44 is located adjacent thetransducing portion of the thin film magnetic transducer 22 and the oneedge of the substrate 20 in intimate engagement with the planarconductive connecting member to form a sub-assembly thereof having apredetermined space between the surface of the superstrate and theselected surface of the substrate 20. A quantity of insulating bondingmaterial which, in the preferred embodiment is formed into a thinelongated rod, is positioned adjacent the predetermined space. Thedimension of the predetermined space is equal to the sum of thethickness of one of the conductive leads 38, 42 or 44, the planarconductive connecting member and the thickness of the diffusableconductive metal coating 68 thereon.

In the preferred embodiment, the insulating bonding material 90 is glasshaving a melted point temperature which is at least 40° C. less than thethermal stress temperature. Typically, the melting point temperature ofthe glass layer is about 455° C. and the thermal stress temperature isabout 500° C.

The so assembled sub-assembly is then subject to the step ofcontrollably heating the sub-assembly in a preselected atmosphere whichinhibits oxidation and corrosion thereof at a heating rate which permitsthe thermal stresses of the sub-assembly to be maintained at a level toavoid damage or permanent distortion to the sub-assembly during heatingthereof up to a bonding temperature located in a bonding temperaturerange between the melting point temperature of the insulating bondingmaterial and below the thermal stress temperature.

One example of a preselected atmosphere used in practicing thisinvention utilized a conveyor furnace which is well known in the art.The conveyor furnace had an internal muffle in the form of an open tube.The internal muffle had a generally rectangular cross-section, forexample a rectangular side of about four (4) inches, a cross-sectionalarea of about sixteen (16) square inches, and a length of about fifteen(15) feet. The preselected atmosphere was formed by continuously purgingthe internal muffle, during the controllably heating step, with nitrogengas having a purity which does not exceed two (2) to three (3) parts ofoxygen per million parts of nitrogen. In this example, the flow rate ofthe nitrogen was about sixty (60) standard cubic feet per minute.Typical heating times for the sub-assembly when transported from theentrance of the muffle to the exit were in the order of about ten (10)hours.

During the controllably heating step, a concurrent step occurs which isthe urging of the superstrate 44 and the substrate 20 of thesub-assembly together with a clamping force illustrated by arrows 80 inFIG. 6 to form a compression boundary between the surface of theconnecting elements, such as for example connecting element 62 in FIG.6, having the diffusable metal coating layer, such as for example thediffusable conductive metal layer 68 in FIG. 6, in intimate contact withthe conductive leads, such as for example conductive lead 38 in FIG. 6,enabling the diffusable conductive metal coating 68 to diffuse into boththe conductive leads and connecting elements to form a diffusedelectrical connection therebetween.

The heated and clamped sub-assembly is maintained at a bondingtemperature within the bonding temperature range for a time periodsufficient to enable the insulating bonding material of the rod 90 tosubstantially fill the predetermined space between the substrate 20 andsuperstrate 44 by capillary action to encapsulate and bond the thin filmmagnetic transducer 22, connecting elements and the conductive leadshaving the diffused electrical connection therebetween into a thin filmmagnetic head assembly.

The schematic representation of FIG. 7 shows the final arrangementbetween the substrate 20, superstrate 44, thin film magnetic transducer22, insulating bonding material 90 within the predetermined space, theconductive lead 68 jointed by a diffused electrical connection of layer68 to the connecting element 62.

After the insulating bonding material 90 has substantially filled thepredetermined space, the sub-assembly is then subject to the step ofcontrollably cooling the same at a cooling rate which permits thethermal stresses of the sub-assembly to be maintained at a level toavoid damage to the sub-assembly during cooling thereof to an ambienttemperature.

FIG. 8 depicts the step wherein the planar conductive connecting memberis positioned with one side of the connecting elements 62, 64 and 66having the diffusable conductive metal coating 68 thereon in intimatecontact with the conductive leads 38, 42 and 44 such that a portion ofthe connecting elements together with the elongated support section 92of the planar conductive connecting member extend passed an edge of thesubstrate 20 other than the one edge adjacent the transducing portion ofthe thin film magnetic transducer. This step occurs in order to 90 fullyencapsulates the thin film magnetic transducer of FIG. 9. A superstrate44 cooperates with the substrate 20 to have the conductive leads 38, theconnecting element 62 and the diffused metal layer 68 extending beyonthe edge of the substrate 20.

FIG. 11 shows the step of lapping the thin film magnetic head assemblyalong the spaced opposed edges of the substrate 20 and superstrate 44 toform a treated surface 102 having a transducing portion of the thin filmmagnetic head exposed as a part thereof. A portion of the gap insulatinglayer 98 may be used to form the gap in the thin film magnetictransducer. This, of course, is not formed as part of this method, butis part of the method of making the thin film magnetic transducer.

The alternate embodiments of FIGS. 11, 12 and 13 envision that theconnecting elements are integral with the conductive leads andelectrical conductors may be affixed to the connecting members at theextended edge, the element 68 being indicitive of such electricallyconductive elements.

In the preferred mode, the diffusable conductive metal may be anydiffusable conductive metal. However, the diffusable conductive metal ispreferrable copper, gold or tin. In practicing this invention it isdesirable that the lead frames and conductors on the thin film magnetictransducer be free and clear of contaminants, oxides, corrosion productsor other such contaminants which would otherwise interfere with thefusion and bonding process.

What is claimed is:
 1. A method of making a thin film magnetic headassembly having a substrate, superstrate and thin film magnetictransducer mounted therebetween wherein the thin film magnetictransducer includes a transducing portion located exterior to adjacentedges of the substrate and superstrate and with conductive leads locatedinterior to and extending between the substrate and superstratecomprising the steps ofmounting on a selected surface of a substrate athin film magnetic transducer with the transducing portion thereoflocated adjacent one edge of said substrate which intersects with saidselected surface; positioning a preformed planar conductive connectingmember having a thickness at least equal to that of the thin filmmagnetic transducer and formed of an elongated support section and aplurality of spaced, aligned connecting elements extending substantiallyperpendicular from the elongated support section wherein the connectingelements include a relatively thin diffusable conductive metal coatinglocated on one side thereof with said one side of the connectingelements having said diffusable conductive metal coating thereon inintimate contact with the conductive leads such that a portion of saidconnecting elements together with the elongated support section of theplanar conductive connecting member extend passed an edge of a substrateother than the one edge adjacent the transducing portion of said thinfilm magnetic transducer; placing a superstrate in alignment with thesubstrate, thin film magnetic transducer and planar conductiveconnecting member such that the one edge of the superstrate is locatedadjacent the transducing portion of the thin film magnetic transducerand the one edge of the substrate in intimate engagement with the planarconductive connecting member to form a sub-assembly thereof having apredetermined space between the surface of the superstrate and theselected surface of the substrate, the dimension of the predeterminedspace being equal to the sum of the thickness of one of the conductiveleads, the planar conductive connecting member and the thickness of thediffusable conductive metal coating thereon; placing a quantity ofinsulating bonding material adjacent the spaced opposed edges and in thevicinity of the transducing portion of the thin film magnetictransducer, said insulating bonding material being selected of amaterial which is electrically and magnetically compatible with the thinfilm magnetic transducer and which has a melting point temperature belowa thermal stress temperature at which at least one of the electricalcharacteristics and the magnetic characteristics of the thin filmmagnetic transducer are permanently distorted; controllably heating thesub-assembly in a preselected atmosphere which inhibits oxidation andcorrosion of the sub-assembly components at a heating rate which permitsthe thermal stresses of the sub-assembly to be maintained at a level toavoid damage to the sub-assembly during heating thereof up to a bondingtemperature located in a bonding temperature range between the meltingpoint temperature of the insulating bonding material and below thethermal stress temperature; during the controllably heating, urging thesuperstrate and the substrate of the sub-assembly together with aclamping force to form a compression boundary between the surface of theconnecting elements having the diffusable metal coating layer inintimate contact with the conductive leads enabling the diffusableconductive metal coating to diffuse into both the conductive leads andconnecting elements to form a diffused electrical connectiontherebetween; and maintaining the heated and clamped sub-assembly at abonding temperature within the bonding temperature range for a timeperiod sufficient to enable the insulating bonding material tosubstantially fill the predetermined space between the substrate andsuperstrate by capillary action to encapsulate and bond said thin filmmagnetic transducer, connecting elements and the conductive leads havingthe diffused electrical connection therebetween into a thin filmmagnetic head assembly.
 2. The method of claim 1 wherein the insulatingbonding material is glass having a melting point temperature which is atleast 40° C. less than the thermal stress temperature.
 3. The method ofclaim 2 wherein the melting point temperature of the glass layer isabout 455° C. and the thermal stress temperature is about 500° C.
 4. Themethod of claim 3 wherein the sub-assembly is heated to a bondingtemperature in a temperature range of about 455° C. to about 500° C. 5.The method of claim 4 further comprising the step ofafter the insulatingbonding material has substantially filled the predetermined space,controllably cooling the sub-assembly at a cooling rate which permitsthe thermal stresses of the sub-assembly to be maintained at a level toavoid damage to the sub-assembly during cooling thereof to an ambienttemperature.
 6. The method of claim 5 comprising the step oflapping thethin film magnetic head assembly along the spaced opposed edges of thesubstrate and superstrate to form a treated surface having a transducingportion of the thin film magnetic head exposed as a part thereof.
 7. Themethod of claim 6 further comprising the step ofattaching anelectrically conductive conductor to the connecting elements.
 8. Themethod of claim 3 wherein the diffusable conductive metal coating iscopper.
 9. The method of claim 3 wherein the diffusable conductive metalcoating is gold.
 10. The method of claim 3 wherein the diffusableconductive metal coating is tin.
 11. The method of claim 4 wherein thepreselected atmosphere is defined by a chamber having an inlet andoutlet and further comprising the step ofpurging the chamber with anitrogen gas having oxygen therein which is less than about 2 parts ofoxygen per million parts of nitrogen.